Process for the preparation of chlorofluoroderivatives of methane

ABSTRACT

A process is disclosed for the preparation of chlorofluorinated methane derivatives by the reaction of a gaseous mixture consisting of (a) methane, chlorine and at least one halogenated hydrocarbon, or (b) carbon tetrachloride and said hydrocarbon, with solid calcium fluoride or with a calcium fluoride-containing substance, (e.g. fluorite) according to the fluid bed technique, wherein the solid calcium fluoride-containing substance is fed in the form of a suspension in at least a portion of the halogenated hydrocarbon, preferably consisting of at least one recycled reaction intermediate product, in the liquid state at a temperature between about 450* and 550* C. The halogenated hydrocarbon consists of one or more of the following halogenated hydrocarbons: CC14, CHC13, CH2C12, CH3C1, CFC13, CHF3, CF2C12, CF3C1, CHFCl2, CHF2C1, C2C14, C2C16, C2HC13. The calcium fluoride-containing solid substance is employed in finely divided form with at least 90 percent of its weight of a size lower than 50 microns.

United States Patent Vecchio et al.

[15] 3,686,338 1 Aug. 22, 1972 [22] Filed:

[54] PROCESS FOR THE PREPARATION OF CHLOROFLUORODERIVATIVES OF METHANE May 8, 1970 [21] Appl. N0.: 35,918

[30] Foreign Application Priority Data May 13, 1969 Italy ..16761 A159 [52] US. Cl ..260/653.8 [51] Int. Cl. ....C07c 17/10, C07c 17/20, C07c 19/08 [58] Field of Search ..260/653.8

[56] References Cited UNITED STATES PATENTS 1,914,135 6/1933 Lacy ..260/653.8 2,739,989 3/1956 Barringer et a1 ..260/653.8

3,206,515 9/1965 Olstowskiet al. ..260/653.8

Primary Examiner-Daniel D. Horwitz Attorney-Stevens, Davis, Miller & Mosher ABSTRACT A process is disclosed for the preparation of chlorofluorinated methane derivatives by the reaction of a gaseous mixture consisting of (a) methane, chlorine and at least one halogenated hydrocarbon, or (b) carbon tetrachloride and said hydrocarbon, with solid calcium fluoride or with a calcium fluoride-containing substance, (e.g. fluorite) according to the fluid bed technique, wherein the solid calcium fluoride-containing substance is fed in the form of a suspension in at least a portion of the halogenated hydrocarbon, preferably consisting of at least one recycled reaction intermediate product, in the liquid state at a temperature between about 450 and 550 C. The halogenated hydrocarbon consists of one or more of the following halogenated hydrocarbons: CC1 CHCI CH Cl CH C1, CFCl CHF CF Cl CF C1, CHFCl CHF CI, C C1,,, C Cl C l-1C1 The calcium fluoride-containing solid substance is employed in finely divided form with at least 90 percent of its weight of a size lower than 50 microns.

7 Claims, No Drawings PROCESS FOR THE PREPARATION OF CHLOROFLUORODERIVATIVES OF METHANE The present invention relates to a process for preparing chlorofluorinated derivatives of methane and more particularly it relates to an improved process for the production of chlorofluorinated derivatives of methane starting from methane and chlorine and by using as the fluorine source calcium fluoride or calcium fluoridecontaining substances (e.g., fluorite) in the presence of halogenated hydrocarbons.

The resulting chlorofluorinated derivatives of methane (CFCl CF Cl etc.) are important products which are of great industrial importance. Such products may be used, amongst other applications, in the field of the so-called aerosol technique and for making foamed products such as for instance urethane foams, as refrigerating liquids, as solvents, etc.

It is already known to prepare chlorofluoro-derivatives of methane by the reactionof CCL, with fluorine in a fluid bed. However, this technique, apart from the necessity of an available hydrocarbon that is already halogenated, has also the drawback of causing agglomeration and/or packing phenomena of the fluorite particles due to the CaCl that forms during the reaction, and which phenomena are extremely detrimental to the satisfactory working of the fluid bed.

It is also well known to prepare chlorofluoro-derivatives of methane by reaction in gaseous phase of methane with chlorine/and a source of fluorine in the solid state, this latter being used according to the fluid bed technique.

In order to improve the fluidizing conditions of the bed there has been suggested the use of solid diluents admixed with the fluorine-containing material, for instance: coal, SiO or A1 but this actually introduces a further complication into the process.

Finally, for solving the problem of an improved fluidization of the fluid bed, there has also been suggested the use of homogeneously granulated fluorinecontaining materials in the form of spheroidal particles, particularly suited for the use in a fluid bed, obtained by the spray-drying of a suspension of a fluoride in 1-1 0 containing small-quantities of CaCl as a binder. The pre-formed spheroidal particles thus obtained may be subsequently fed into a chlorofluorination reactor working according to the fluid bed technique.

Thus, an object of the present invention is to provide a still further improved process for the preparation of chlorofluoro-derivatives of methane by the reaction in the gaseous phase of a mixture consisting of methane and chlorine with calcium fluoride or with a calcium fluoride-containing substance (such as fluorite) in the solid state according to the fluid bed technique.

Another object of this invention is to provide a process for the preparation of chlorofluoro-derivatives of methane the thermal parameters of which are readily controllable, and that will allow high reaction rates while being simple to work and of good efficiency.

These and still other objects which will appear more clearly to the skilled in the art from the following description can be achieved, according to the present invention, through an improved process for the preparation of chlorofluoro-derivatives of methane byv the reaction of a gaseous mixture consisting essentially of methane, chlorine and at least one halogenated hydrocarbon, or consisting essentially of carbon tetrachloride and said halogenated hydrocarbon, with solid calcium fluoride or with a calcium fluoride-containing substance, according to the fluid bed technique, at temperatures between 450 and 550 C., wherein the solid substance used which contains calcium fluoride and has a granulometry for at least percent by weight below 50 microns, is fed into the reactor in the form of a suspension in at least a portion of the halogenated hydrocarbon in the liquid state, preferably consisting of at least one recycled reaction intermediate product.

By operating according to the present invention, because of the reaction between methane, chlorine and calcium fluoride, calcium chloride is formed which acts as binder on the particles fed in suspension, thereby facilitating the growth of the preexisting granules as well as the formation of new substantially spheroidal granules, particularly suited for a fluid bed.

The process may be carried out at temperature between 450 and 550 C., as already mentioned above, and with contact times of the gaseous phase with the calcium fluoride bed which may vary within wide limits, up to values around 60 seconds, since from these contact times largely depend both the formation and the size-distribution of the granules depend the fluid bed, as well as the conversion yield of the methane into the desired chlorofluoro-derivative.

The granulometry of the calcium fluoride fed is, in general, between 1 micron and 44 microns, for practical reasons in the grinding operation.

The calcium fluoride is employed in a substantially stoichiometric molar ratio, although an excess is not harmful for the process. The chlorine and the methane are introduced into the reactor at a molar ratio Cl CH between 3.5 and 4.5.

The halogenated hydrocarbon is selected from the class consisting of the reactants, the intermediates, the products and by-products of the reaction containing from 1 to 2 carbon atoms. The halogenated hydrocarbons in question preferably consist of mixtures of two or more of the following compounds: CCl CHCl CH CI CFCl CHF CF Cl CF Cl, CHFCI CHF2CI, C2Cl C Cl C2HCI3, etc.

The composition of the mixture of halogenated hydrocarbons, that is preferably recycled, may vary within wide limits, depending on the reaction conditions and in relation to the composition of the desired upon the heat regulation requirements, and upon the products that one mainly wishes to obtain.

Moreover, the concentration of the solid (calcium fluoride) in the halogenated hydrocarbon in the liquid state, is also related to the type and characteristics of the feeding system used. Finally, the technique which is the object of this invention may be applied either in a single stage fluid bed reactor or in successive stages with more than one fluid bed.

According to one preferred, although not the only, embodiment of the invention, the process is carried out by feeding into the reactor, besides methane, chlorine and, if desired, a part of the halogenated hydrocarbon in gaseous phase, the calcium fluoride in the form of a suspension in part of or in the whole halogenated hydrocarbon in the liquid state. The reaction products are then recovered and separated according to various methods well known in the art.

The pressure at which the reaction is conducted is not a critical parameter and may be maintained at substantially atmospheric values Thanks to the simple operational conditions, the process turns out to be particularly convenient.

One advantage lies in the possibility of carrying out the chlorofluorination reaction of the methane simultaneously with the granulation of the calcium fluoride, fed in the form of a suspension in the halogenated hydrocarbon in the liquid state, thereby avoiding the preliminary operation of preparing the granular calcium fluoride bed and the corresponding expenditure of the required energy (evaporation, etc.).

Still another advantage lies in the fact that the evaporation of the liquid halogenated hydrocarbon, wherein the calcium fluoride is suspended, is particularly helpful for, absorbing the considerable quantity of heat developed by the reaction. As a matter of fact, the chlorofluorination reaction of the methane is exothermic and, thus, when carrying out the process, it is necessary to provide for the dissipation of part of the heat that has been freed. This heat dissipation, carried out by conventional methods known in the art, may be achieved conveniently by suitably regulating the quantity of liquid halogenated hydrocarbon used, whose evaporation thereby contributes to the thermal regulation of the whole system.

A further particularly interesting advantage afforded by this invention resides in the possibility of feeding the calcium fluoride or the product containing it in the most suitable granulometric size, that is, in a particularly fine size (since it is known that the reactivity of the calcium fluoride is related among other things to its size), as actually occurs when operating according to this invention where the calcium fluoride, after the evaporation of the liquid halogenated hydrocarbon wherein it is suspended, finds itself in the reaction medium in particles of fine size having a high reactivity.

Finally, further advantages are represented by the easy feeding of the solid calcium fluoride in suspension in the liquid halogenated hydrocarbon achieved by means of pumps, even when within the reactor there are overpressures, and by the contemporaneous granulation of the calcium fluoride into spheroids particularly suited for the fluid bed technique.

In any event, the calcium fluoride that is not retained in the reactor may be recovered by means of conventional methods and recycled, thereby increasing the granulation yield of the system.

The invention will now be further described through the following examples given by way of illustration: Two types of tests were carried out:

a. Chlorofluorination of CH, with chlorine and fluorite, in the presence of a recycle consisting of liquid CO, in which the fluorite has been suspended (Examples 1 and 2).

b. Fluorination of CCl, with fluorite fed in the form of a suspension in one part of the liquid CC], (Example 3).

In Example 3, carried out under the same feeding conditions of the fluorite of Examples 1 and 2, but starting from CC]., and fluorite, it is particularly apparent how there occurs a simultaneous reaction of the fluorite and its granulation, according to the spirit of the invention, even in the presence of halogenated methane derivatives instead of the methane and chlorine of Examples 1 and 2.

Both types of tests started from a fluid bed of fluorite, granulated according to the prior art, into which had been sprayed the fluorite suspension in the liquid recycle.

The apparatus wherein the tests were carried out batchwise consisted of the feeding lines for the reactants, a fluid bed reactor having in its lower part a spray-nozzle, and a product-gathering system.

The feeding lines for CH chlorine and nitrogen were of a conventional type and fitted with a flask, a flow-rate meter and a pressure gauge.

The feeding line for the gaseous recycle consisted of a storage vessel, a metering pump, a pressure gauge and an evaporator.

The feeding line for the fluorite suspension in the liquid recycled halogenated hydrocarbon consisted of a storage tank fittedwith a stirrer, a metering pump for slurries and a pressure gauge. The different feeding lines discharged together into the sprayer.

The reactor itself was a cylinder with a conical bottom and a diameter of 50 mm, made of Ni alloy, provided with a sheath allowing the temperature to be measured and it was heated electrically from the outside. In the upper part of the reactor there was placed a filter for retaining the smaller particles of solid drawn out of the fluid bed by the gaseous flow.

The sprayer, located immediately upstream of the reactor, was formed of three concentric cylindrical chambers. Through the innermost chamber there was fed the suspension, through the mid chamber there flowed the chlorine kept at room temperature, while into the outermost chamber there was fed the methane, and if desired the methane in admixture with a part of the recycled halogenated hydrocarbon in vapor phase. The sprayer worked also as a mixer for the methane and gaseous recycled halogenated hydrocarbon mixture of the outer chamber and the chlorine of the mid chamber. In the fluorination test of the CCL, (Example 3) the suspension of fluorite in the liquid CCl, was fed into the inner chamber similarly to the chlorofluorination tests upon the CH into the mid chamber there flowed in nitrogen while the outer chamber, obviously, remained unused.

The collection system for the products consisted of a water-cooled condenser, a washing vessel for washing with water and a washing vessel for washing with NaOH solution. The organic phase collected in the two washing vessels was analyzed by gas chromatography. In the following examples, there was initially loaded into the reactor a mixture of CaF and CaCl in the form of preformed spherical granules, granulated according to methods well known per se in the prior art.

The mass was maintained fluid during the heating by means of a nitrogen stream, until reaching the operational value. At this point there were fed the reactants and at the same time there was interrupted the feeding EXAMPLE 1 Chlorofluorination of CH,

Test conditions: Temperature 500C. Pressure 1 atm. Inside reactor crosssectional area i 18.8 sq.cm. Linear feed rate 24 cm/sec. Contact time 1.05 sec. Molar ratio:recyclelcl jCl-l 20/4/1 Composition of recycle CCL,

Composition of the suspension:

Fluorite 11.6% b.w. (grams) Liquid CCl. 88.4% b.w. (grams) Duration of test 60 min. Molar ratio:recyc1e gas/recycle liquid 1.07

Balance of the solid phase A) Initial Balance: Granul- Weight of b.w. of b.w. CaCl Cal total ometry in g of CaCl of CaF, moles moles moles 246-495 Microns 600 92.0 8.0 4.970 0.616 5.586 15 Microns 200 100 2.563 2.563 Total 800 4.970 3.179 8.149

"This quantity was fed as a suspension B) Final Balance: Granul- Weight b.w. b.w. CaCl CaF, total ometry in of CaCl of CaF moles moles moles Microns g 74-175 18 45.0 55.0 0.073 0.127 0.200 175-246 45 58.2 41.8 0.236 0.242 0.478 246-495 619 80.3 19.7 0.480 1.565 6.045 495-701 65 70.5 29.5 0.413 0.246 0.659 701-991 52 57.0 43.0 0.267 0.288 0.555 Total 809 5.483 2.577 8.060

"This quantity was collected on the filter located in the upper part of the reactor and it was found that it had the same granulometry as the fluorite fed in suspension.

Initial moles(CaF,+CaCl Final moles (CaF +CaCl,) 8.060 Lost moles (CaF +CaCl,) 0.089 (3.5% with respect to the fluorite fed in suspension).

Final moles CaCl, 5.483

0.513 (corresponding to a conversion of 20% with respect to the fluorite fed in suspension).

Initial moles CaCl, Formed moles CaCl,

The quantity of formed chlorofluoromethanes, calculated by means of gas-chromatographic analysis, turned out to be:

0.040 moles of CF Cl 0.904 moles of CFCl;

Thus, the conversion of the CH to CFCl amounted to percent while the conversion of the CH to CF Cl amounted to 4 percent.

EXAMPLE 2 Chlorofluorination of Cl-l Test Conditions: Temperature 500C Pressure 1 atm. Inside reactor cross- 18.8 sq. cm. sectional area Linear feed rate 25 cm/sec. Contact time 2 sec. Molar ratio: recyCIe/CI CH 7/4/1 Composition of recycle CCl Composition of suspension:

Fluorite 12.2% b.w. (grams) Liquid CC! 87.8% b.w. (grams) Duration of the test 45 min. Molar ratio gas recycle/liquid recycle 0.67

Balance of the solid phase: A) Initial balance Granul- Weight b.w. b.w. Moles Moles total ometry in of CaCl of CaF, CaCl CaF 276495 microns 1180 90.5 9.5 9.625 1.437 11.062 l5 microns 150 1.923 1.923 Total 1330 9.625 3.360 12.985

""1 his quantity was fed in as a suspension.

B) Final balance: Granul- Weight b.w. of b.w. Moles Moles Total ometry in of of CaCl, CaF Moles Microns g CaCl CaF 1-5 5 18.5 91.5 0.008 0.059 0.067 74-175 16 51.0 49.0 0.074 0.101 0.175 176-246 35 75.2 24.8 0.237 0.111 0.348 246-495 1219 87.1 12.9 9.558 2.016 11.574 495-701 45 85.0 15.0 0.345 0.087 0.432 701-991 30 80.5 19.5 0.218 0.075 0.293 Total 1350 10.440 2.449 12.889

This quantity was collected on the filter placed in the upper part of the reactor, and it was found it had the same granulometry as the fluorite fed in suspension.

lnitial moles(CaF,+ CaCl,) 12.985

Final moles (CaF,+ CaCl,) 12.889

Lost moles (CaF,+ CaCl,) .096 (5% with respect to the fluorite fed in suspension).

To this loss, with regard to the granulation yield of the test, there must be added the quantity of solid collected on the filter, corresponding to 3.5 percent with respect to the fluorite fed in suspension, wherefore the quantity of fluorite that was granulated amounted to about 91.5 percent of the fed fluorite.

of about 42% with respect to the fluorite fed in suspension The quantity of formed chlorofluoromethanes, calculated from analysis by gas-chromatography, was found to be:

0.058 Moles of CF CI 1.474 Moles of CFCI;

Wherefore it turned out that the conversion of the CH to CFCl amounted to 88.8 percent while the conversion of CH, to CF Cl amounted to 3.5 percent.

EXAMPLE 3 Fluorination of CCl Test Conditions: Temperature 500C Pressure 1 atm. Inside reactor crossaectional area 18.8 sq.cm. Linear feed rate 25 cm/sec. Contact time 1 sec. Molar ratio2CCL/N, 2 Composition of the suspension:

Fluorite 10.3% b.w. (grams) Liquid CCI. 89.7% b.w. (grams) Duration of the test 56 min.

Balance of the solid phase A) Initial balance Granul- Wei'ght b.w. b.w. Moles Moles Total ometry g1 EEC 6211 CaCl Cal", moles 246-495 microns 592 87.2 12.8 4.651 0.970 5.621 1-5 240 m abt. 3.074 3.074 microns 100% Total 832 4.651 4.044 8.695

"Ihis quantity was fed as a suspension.

B) Final balance: j Granul- Weight. luv. b.w. Moles Moles Total ometry in of of CaCl, CaF, moles Microns g CaCl, CaF,

l-5 13 17.4 82.6 0.020 0.138 0.158 74-175 20 50.2 49.8 0.090 0.128 0.218 175-246 52 60.7 39.3 0.284 0.262 0.546 246-495 626 75.4 24.6 4.252 1.972 6.224 495-701 20 68.5 31.5 0.123 0.08l 0.204 701-991 102 57.7 42.3 0.530 0.553 1.083 991-1397 17 56.2 43.8 0.086 0.095 0.181 Total 850 5.385 3.229 8.614

""This quantity was collected on the filter and it was found to have the same granulometry as the initial fluorite fed in suspension.

the fluorite fed in suspension) To this loss, with regard the granulation yield of the test, there must be added the quantity of solid collected on the filter located in the upper part of the re 0- tor, corresponding to 5.1 percen with respect to t e fluorite fed in suspension, wherefore the quantity of fluorite which was granulated amounted to 92.3 percent of the fed fluorite.

Final moles CaCl, 5.385 Initial moles CaCl, 4.651 Formed moles CaCl, 0.734 (corresponding to a conversion of 23.1% with respect to the fluorite fed in suspension).

The quantity of chlorofluoromethanes thus formed,

0.080 moles of Cl- ,Cl 1.252 moles of CFC];

Thus, the conversion of the CCL, to CFCI amounted to 9.2 percent and conversion of the CCL, to CF CI amounted to 0.6 percent.

What is claimed is:

1. In a process for the preparation of chlorofluoromethane derivatives by the reaction of a gaseous mixture comprising methane, chlorine and at least one halogenated hydrocarbon selected from the group consisting of chloromethanes, fluoromethanes, chlorofluoromethanes, chloroethanes, or a gaseous mixture comprising tetrachloromethane and the abovesaid halogenated hydrocarbons with calcium fluoride or with a solid substance consisting essentially of CaF according to fluid bed techniques, the improvement comprising feeding the solid CaF containing substance, at least percent of which has a particle size lower than about 50 microns, in the form of a suspension in at least a portion of said halogenated hydrocarbon, in the liquid state, at a temperature between about 450 and 550 C.

2. A process according to claim 1, wherein the halogenated hydrocarbons consist essentially of halogenated hydrocarbons selected from the class consisting of the reactants, the intermediates, the products and the by-products of the reaction.

34A process according to claim 1, wherein the halogenated hydrocarbons are selected from the class consisting of CCl.;, CHC1 CH Cl CH Cl, CFCl CHF CF Cl CF Cl, CHFCI CHF CI, C Cl and C2HC13.

4. A process according to claim 1, wherein the calcium fluoride-containing substance is fluorite.

5. A process according to claim 1, wherein the reaction is carried out with a molar ratio of Cl,jCI-I between about 3.5 and 4.5.

6. A process according to claim 1, wherein the process is carried out in successive stages comprising successive fluid beds.

7. A process according to claim 1, wherein the halogenated hydrocarbon is at least a recycled compound selected from the class consisting of the reactants, the intermediates, the products and the byproducts of the reaction. 

2. A process according to claim 1, wherein the halogenated hydrocarbons consist essentially of halogenated hydrocarbons selected from the class consisting of the reactants, the intermediates, the products and the by-products of the reaction.
 3. A process according to claim 1, wherein the halogenated hydrocarbons are selected from the class consisting of CCl4, CHCl3, CH2Cl2, CH3Cl, CFCl3, CHF3, CF2Cl2, CF3Cl, CHFCl2, CHF2Cl, C2Cl6 and C2HCl3.
 4. A process according to claim 1, wherein the calcium fluoride-containing substance is fluorite.
 5. A process according to claim 1, wherein the reaction is carried out with a molar ratio of Cl2/CH4 between about 3.5 and 4.5.
 6. A process according to claim 1, wherein the process is carried out in successive stages comprising successive fluid beds.
 7. A process according to claim 1, wherein the halogenated hydrocarbon is at least a recycled compound selected from the class consisting of the reactants, the intermediates, the products and the by-products of the reaction. 